The Croatian media is alleging that world No. 15 Marin Cilic tested positive for a banned substance at the Munich tournament in April and is already serving a three-month suspension.

Reports say that Cilic took some kind of glucose supplement that contained a banned substance. A highly-placed source in Croatia told TENNIS.com that the reports are more than likely accurate.

The 24-year-old Cilic was said to have been told by the ITF before his Wimbledon second-round match against Kenny De Schepper that he had tested positive and subsequently pulled out, citing an injury sources say was dubious.

Cilic, who reached the Queen's Club final before Wimbledon, is said to be cooperating with the ITF. It is unclear when Cilic will be able to return. Some Croatian reports have it that it could be as early as next month.